(1) Field of the Invention
The present invention relates to an infrared spectrum measuring apparatus, and more particularly to an infrared spectrum measuring apparatus adapted for measuring the absorption of infrared radiation by a liquid sample utilizing a total reflection phenomenon of light.
(2) Description of the Prior Art
Regarding conventional infrared spectroscopic analysis, a report dealing with the increasing of the infrared absorption of a sample by enhancing the intensity of an electric field component of infrared radiation using a metal provided on an attenuated total reflection has been described in Applied Spectroscopy 44 (1990), pp 512-518. In this paper, it is discussed that when a sample layer of molecules with high molecular weight is mounted on an attenuated total reflection prism and further a metal layer formed on an elastic membrane is provided via an air gap, the infrared absorption by the sample is increased by a sandwich effect due to a difference in refractive indices.
Because sensitivity in the foregoing conventional art depends greatly on the thicknesses of the sample and the air gap, unless the thicknesses of the sample and air gap are precisely controlled with a precision of some several nm, infrared absorption spectra cannot be obtained with a better reproducibility, thereby it is difficult to carry out any quantitative analyses without taking some effective measures to solve such problems. Further, hereinabove only a sample layer of molecules with high molecular weight is addressed and measurement of any liquid sample is not taken into account.